The overall objective of the proposed research is to better understand the effects, as well as the limitations, of cognitive factors in human autonomic classical conditioning. Three experiments are proposed. 1. The first experiment will attempt to objectively measure the complex cognitive processing demands which occur during differential autonomic classical conditioning. The cognitive processing demands will be measured at specific points in time following the reinforced CS+ and the nonreinforced CS- by means of a probe reaction-time technique. 2. The second experiment will test for cognitive/autonomic dissociations during the acquisition and extinction of classically conditioned autonomic responses. "Potentially phobic" stimuli will be used and extinction instructions will be manipulated in order to optimize the possible dissociations. 3. The third experiment involves the use of a dichotic listening procedure to test for unaware acquisition, performance, and generalization of previously conditioned autonomic responses.